1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an inductive-type magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
Improvements in the performance of a thin-film magnetic head are sought since a surface recording density of a hard disk device has been improved. A composite thin-film magnetic head having a structure in which, a recording head having a inductive-type magnetic transducer for writing and a reproducing head having a magneto resistive (referred as MR) element for reading are stacked is broadly used as the thin-film magnetic head. The MR element includes an device using an effect of anisotropic magneto resistive (referred as AMR) and another device using an effect of giant magneto resistive (referred as GMR). The reproducing head using the AMR element is called an AMR head or simply MR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is over 1 gigabit per square inch, and the GMR head is used as the reproducing head whose surface recording density is over 3 gigabit per square inch.
The AMR head has an AMR film having the AMR effect. The GMR head has a structure identical to the AMR head except that a GMR film having the GMR effect is used instead of the AMR film. However, when the same external magnetic field is applied, the GMR film exhibits greater change in resistance than the AMR film. As a result, the GMR head can increase the reproduction output three to five times the AMR head.
A method is disclosed in which the AMR film being used as the MR film is exchanged with a material with better reactive magnetic resist such as GMR film, and a method in which a pattern width of the MR film, especially the MR height are used as the methods of improving the performance of the reproducing head. The MR height is a length (height) from an edge of air bearing side to an edge of the other side, and it is controlled by an etching amount of the air bearing surface. The air bearing surface, here, is facing a magnetic recording medium and called a track surface as well.
On the other hand, performance improvements in a recording head have been discussed while performances in a reproducing head has improved. A factor which determines the performance of the recording head is a throat height (TH). The throat height is a length (height) of a pole between the air bearing surface and an edge of an insulator which electrically isolates a thin-film coil for generating magnetic flux. A reduction of the throat height is needed in order to improve the recording head performance. The throat height is controlled by an etching amount when the air bearing surface is processed.
To improve a recording density among the performance of the recording head, a track density of magnetic recording medium is required to be increased. In order to achieve this, a recording head with a narrow track structure in which a width of the top and bottom pole on the air bearing surface, which are formed on top and bottom sandwiching a write gap, is reduced from some microns to sub-microns. Semiconductor process techniques are employed to achieve the narrow track structure.
A method of manufacturing the composite thin-film magnetic head as an example of method of manufacturing the thin-film magnetic head of the related art will be described by referring to FIG. 39 through FIG. 44.
As shown in FIG. 39, an insulating film 102 made of alumina (Al2O3), for example, of about 5 to 10 xcexcm in thickness is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. A bottom shield layer 103 for a reproducing head is formed on the insulating film 102. A shield gap film 104 is formed on the bottom shield layer 103 by depositing alumina 100 to 200 nm in thickness through sputtering. An MR film 105 of tens of nanometers in thickness for making up the MR element for reproduction is formed on the shield gap film 104, and a desired shape is obtained by patterning through photolithography with high precision. Next, after forming a lead layer (not shown) on both sides of the MR film 105 as an extraction electrode layer which is electrically connected to the MR film 105, a shield gap film 106 is formed on the lead layer, the shield gap film 104 and the MR film 105, and then the MR film 105 is buried in the shield gap film 104 and 106. Further, a top shield serving as a bottom pole (referred as bottom pole in the following description) 107 made of magnetic materials such as permalloy (NiFe) used for both reproduction and recording head is formed on the shield gap layer 106.
As shown in FIG. 40, an insulating film such as a write gap layer 108 made of alumina film is formed, for example, on the bottom pole 107, and a photoresist layer 109 in a desired pattern is formed on the write gap layer 108 through photolithography with high precision. Next, a thin-film magnetic coil 110 as a first layer for an inductive recording head made of, for example, copper (Cu) is formed on the photoresist layer 109 by, for example, plating method. A photoresist layer 111 in a desired pattern is formed covering the photoresist layer 109 and the coil 110 through photolithography with high precision. Next, a heat treatment at 250xc2x0 C., for example, is applied to have the coil 110 flattened and have turns of the coil 110 insulated from each other. Further, a thin-film coil 112 as a second layer made of, for example, copper is formed by plating method. A photoresist layer 113 in a desired pattern is formed on the photoresist film 111 and the coil 112 through photolithography with high precision, and a heat treatment at 250xc2x0 C. is applied to have the coil 112 flattened and have turns of the coil 112 insulate from each other.
As shown in FIG. 41, an opening 108a is formed by partially etching the write gap layer 108 in a position behind the coil 110 and 112 (right-hand side in FIG. 41) in order to form a magnetic path. Further, a top yolk-cum-top pole (referred as a top pole in the following description) 114 made of magnetic materials for recording head such as permalloy is selectively formed on the write gap layer 108, the photoresist layers 109, 111 and 113. The top pole 114 has a contact with the bottom pole 107 in the opening 108a being magnetically coupled. Next, after the write gap layer 108 and the bottom pole 107 are etched about 0.5 xcexcm by ion milling etching using the top pole 114 as a mask, an overcoat layer 115 made of such as alumina is formed. The thin-film magnetic head is completed after a track surface (air bearing surface) 120 of the recording head and reproducing head are formed by applying machine grinding with a slider.
FIG. 42,43, and 44 illustrate a completed configuration of the thin-film magnetic head. Here, FIG. 42 shows a sectional view of the thin-film magnetic head orthogonal to the air bearing surface 120, and FIG. 43 is an enlarged cross-sectional view of parallel to the air bearing surface 120 and FIG. 44 is a plan view. FIG. 39 to 42 show a cross section taken along the line Axe2x80x94Axe2x80x2 in FIG. 44. An illustration of the overcoat layer 115 is omitted in FIG. 42 to 44.
It is important to form the throat height (TH), an apex angle (xcex8), a pole width (P2W) and a pole length P2L shown in FIG. 42 and 43 precisely in order to improve the performance of the thin-film magnetic head. The apex angle xcex8 is an angle between the corner of the track surface of the photoresist layer 109, 111 and 113, and a straight line connecting the surface of the top pole 114. The pole width P2W provides a width of a recording track in a recording medium. The pole length P2L represents the thickness of the pole. Further, in FIG. 42 and 44, xe2x80x98TH0 positionxe2x80x99 represents a reference position 0 of the throat height, that is, a position of a track-side edge of the photoresist layer 109 which is an insulating layer, electrically isolating the thin-film coils 110 and 112 from each other.
As shown in FIG. 43, a structure in which each sidewall of the top pole 114, the write gap layer 108 and a portion of the bottom pole 107 is vertically formed in a self-aligned manner is called a trim structure. The trim structure prevents an increase of the effective track width occurred through expansion of the magnetic flux generated during writing of a narrow track. As shown in FIG. 43, a lead layer 121 as an extraction electrode layer being electrically connected to the MR film is provided on both sides of the MR film 105. However, an illustration of the lead layer 121 is omitted in FIG. 39 to 42 and 44.
FIG. 45 illustrates a plan structure of the top pole 114. As shown in the illustration, the top pole 114 consists mostly of a yolk area 114 a and a pole tip 114b having almost a constant width W1 as the pole width P2W. At a coupling point of the yolk 114a and the pole tip 114b, an outer frame of the yolk 114 has an angle xcex1 against a surface parallel to the air bearing surface 120, while an outer frame of the pole tip 114b has an angle xcex2 against the surface parallel to the air bearing surface 120. Here, a is, for example, about 45 degrees and xcex2 is 90 degrees. The width of pole tip 114b defines the width of the recording track. The pole tip 114b includes an area F in front of the TH0 position (air bearing surface 120 side) and an area R behind the TH0 position (yolk 114a side). As shown in FIG. 4, the area F is constant on the flat surface of the write gap layer 108, the area R and the yolk 114a are constant on an coil area (referred as apex in the following description) being swelled up, covered by the photoresist film 109, 111 and 113. 16. The publication relating to the shape of the top pole is, for example, Japanese Patent application Laid-open Hei 8-249614 (U.S. Pat. No. 5,600,519).
Since the pole width P2W determines the track width of the recording head, the pole width P2W needs to be formed precisely. Especially, recently, to make high surface density recording possible, that is to form the recording head having a narrow track structure, micro lithography having a size of the pole width P2W of the top pole equal to or less than 1.0 xcexcm is required.
As a method of forming the top pole, shown in, for example, Japanese Patent Application Laid-open Hei 7-262519 (U.S. Pat. No. 5,438,747), frame plating method is used. In a case where the top pole 114 is formed by frame plating method, a thin electrode film made of, for example, permalloy is formed all over the apex area by, for example, sputtering. Next, after applying a photoresist on it, a pattern is obtained through lithography procedure to form a frame (outer frame) for plating. The top pole 114 is formed by plating method having the electrode film as a seed layer.
By the way, the apex area and the other areas have, for example, more than 7 to 10 xcexcm difference in heights. A photoresist of 3 to 4 xcexcm in thickness is applied on the apex area. If the photoresist with equal to or more than 3 xcexcm in film thickness on the apex is needed, a photoresist film with for example, equal to or more than 8 to 10 xcexcm in film thickness is formed in the lower part of the apex area since the photoresist with liquidity gathers into a lower area.
To form a narrow track as described above, a frame pattern with a width of about 1.0 xcexcm depending on the photoresist film is needed to be formed. That is, micro pattern with a width of 1.0 xcexcm or less has to be formed depending on the photoresist film with equal to or more than 8 to 10 xcexcm in thickness. However, forming the photoresist film with such a thick film with a narrow pattern width has been difficult.
Further, during an exposure of photolithography, a light for the exposure reflects with the undercoat electrode film as a seed layer and the photoresist is exposed by the reflecting light. As a result, deformation of the photoresist pattern occurs and so that a sharp and precise photoresist pattern can not be obtained. Consequently, the top pole can not be formed in a desired shape since sidewalls of the top pole take a shape being rounded. Especially, as shown in FIG. 8, when the top pole width P2W is made further narrower to have W1xe2x80x2, the desired width W1xe2x80x2 becomes harder to obtain. It is because the width of the photoresist pattern defining the top pole width P2W is wider than the desired value and the shape becomes the one shown with a dotted line in FIG. 8 since among the pole tip area 114b, in an area R being placed on the apex area, the reflecting light being reflected from the undercoat electrode film includes not only the reflecting light of orthogonal direction but the reflecting lights of diagonal direction or lateral direction from the slope of the apex area resulting in giving an influence to photosensitivity of the photoresist layer. Among the pole tip area 114b, a width of the area F is an extremely important factor in defining the track width on the recording medium. As a result, if the width of the area F becomes wider than the value W1xe2x80x2 described above, the narrow track width as desired can not be obtained.
Same problems exists in the magnetic head claimed in the Japanese Patent Application Laid-open Hei 8-249614. It is because the width of the front area of the TH0 position cannot be controlled precisely under the influence of an exposure of the photoresist layer given by the reflecting light from a slope of the apex area in diagonal and lateral direction since the pole width from the TH0 position to the yolk area changes moderately.
As shown in FIG. 46, the connecting area R from the TH0 to the yolk area 114a of the pole tip area 114b has about the same width with the front area of the TH0 having a small cross sectional view area, the magnetic flux from the yolk area 114a is saturated in the area R so that the flux can not sufficiently reach the area F which determines the track width. For that, an overwrite characteristic, that is, a characteristic in a case where a data is written on a recording medium over the already-written data, becomes as low as 10 to 20 dB so that a sufficient overwrite characteristic can not be obtained.
A publication relating to the present invention includes Japanese Patent Application Laid-open Hei 1-184611 and Japanese Patent Application Hei 10-188225. An inductive thin-film magnetic head having a magnetic core which comprises a rectangular pole tip with about the same width with a track width facing a magnetic medium and a back core having a wide cross sectional area of the pole tip, and an angle between the pole tip and the back core is about 90 degrees is claimed in the Japanese Patent Application Laid-open Hei 1-184611. In the Japanese Patent Application Laid-open Hei 10-188225, a inductive thin-film magnetic head is disclosed. In the magnetic head, a projected area which determines the track width is formed on one side of the pole film, and the size of each portion of the projected area is set to a specific value.
The present invention is designed to overcome the forgoing problems. It is an object of the invention to provide a thin-film magnetic head in which precise control of the pole width is performed and, at the same time, a sufficient overwrite characteristic can be obtained even in a case where the pole width is reduced.
A thin film magnetic head of the invention includes a first insulating layer as a write gap layer, and a second insulating layer provided in a predetermined area on a recording medium side in contact with a surface of the first insulating layer. First and second magnetic layers include two magnetic poles which face each other with the first insulating layer in between, and are positioned to face with a recording medium. The first and second magnetic layers being magnetically coupled to each other in a back gap area on an opposite side of an air-bearing surface facing the recording medium, and the first magnetic layer has a magnetic pole tip which in turn has a uniform width portion for defining a write track width on the recording medium. The magnetic pole tip extends from the air-bearing surface to a predetermined position on the second insulating layer in contact with the surfaces of the first and second insulating layers. A magnetic pole coupler is located in the back gap area in contact with the second magnetic layer and a yoke which magnetically couples the magnetic pole tip with the magnetic pole coupler. A thin film coil is located between the first and second magnetic layers, and a third insulating layer covers an inner surface of a recessed space surrounded by the first and second insulating layers, the magnetic pole tip and the magnetic pole coupler. In the thin film magnetic head, a recording-medium-side edge of the second insulating layer defines a reference position to the air-bearing surface, and a surface of the magnetic pole tip, the surface being on a side opposite to the first insulating layer, and edge surfaces of the third insulating layer are planarized in one plane.
The invention also includes a method of manufacturing a thin film magnetic head having the steps of forming a first insulating layer as a write gap layer, providing a second insulating layer in a predetermined area on a recording medium side in contact with a surface of the first insulating layer and forming first and second magnetic layers to be magnetically coupled to each other in a back gap area on an opposite side of an air-bearing surface facing the recording medium. The first and second magnetic layers include two magnetic poles which face each other with the first insulating layer in between and are positioned to face with a recording medium, and the first magnetic layer has a magnetic pole tip which has a uniform width portion for defining a write track width on the recording medium. The magnetic pole extends from the air-bearing surface to a predetermined position on the second insulating layer in contact with the surfaces of the first and second insulating layers. A magnetic pole coupler is located in the back gap area in contact with the second magnetic layer and a yoke which magnetically couples the magnetic pole tip with the magnetic pole coupler. The method forms a thin film coil between the first and second magnetic layers, and forms a third insulating layer to cover an inner surface of a recessed space surrounded by the first and second insulating layers, the magnetic pole tip, and the magnetic pole coupler. Then, a surface of the magnetic pole tip is planarizing to form one plane with at least edge surfaces of the third insulating layer, the surface of the magnetic pole tip being on a side opposite to the first insulating layer. The second insulating layer is formed so that a recording-medium-side edge of the second insulating layer defines a reference position to the air-bearing surface in the step of forming the second insulating layer.
A thin-film magnetic head of the invention includes at least two magnetic layers magnetically coupled to each other including two magnetic poles in part of sides of the area facing a recording medium, the magnetic poles being opposed to each other with a gap layer in between; and a thin-film coil unit placed between the magnetic layers with an insulating layer in between. At least one of the two magnetic layers including: a first magnetic layer portion with a constant width for defining a width of a recording track of a recording medium extending from a recording medium opposite surface facing to the recording medium to an edge of the insulating layer closer to the recording medium or its vicinity; and a second magnetic layer portion magnetically coupled to the first magnetic layer portion at the edge of the insulating layer or its vicinity. A step in the width direction is formed in a coupling point of the first magnetic layer portion and the second magnetic layer portion so as to have a width of the first magnetic layer portion at the coupling point smaller than a width of the second magnetic layer portion at the coupling point.
A method of manufacturing the thin-film magnetic head of the invention includes a step of forming at least two magnetic layers magnetically coupled to each other including two magnetic poles in part of sides of the area facing a recording medium, the magnetic poles being opposed to each other with a gap layer in between; and a step of forming a thin-film coil unit between the magnetic layers with an insulating layers in between. At least one of the magnetic layers is formed so as to include a first magnetic layer portion with a constant width for defining a width of a recording track of a recording medium extending from a recording medium opposite surface facing to the recording medium to an edge of the insulating layer closer to the recording medium or its vicinity, and a second magnetic layer portion magnetically coupled to the first magnetic layer portion at the edge of the insulating layer or its vicinity; and a step in the width direction is formed in a coupling point of the first magnetic layer portion and the second magnetic layer portion so as to have a width of the first magnetic layer portion at the coupling point smaller than a width of the second magnetic layer portion at the coupling point.
In the thin-film magnetic head or the manufacturing method of the same of the invention, the recording track width of the recording medium is defined according to the specific width of the first magnetic layer portion. The first magnetic layer portion is magnetically coupled to the second magnetic layer portion whose width is wider than that of the first magnetic layer portion at the edge close to the recording medium in the insulating layer or its vicinity, and a step in the direction of the width is formed at the coupling point.
Further, the step face of the second magnetic layer portion at the coupling point may be substantially orthogonal to the extending direction of the first magnetic layer portion.
Further, the edges of the step face of the second magnetic layer portion may be rounded off.
Further, the width of the second magnetic layer portion may be almost constant all through the area.
Further, the width of the second magnetic layer portion may differ depending upon the position.
Further, the width of the second magnetic layer portion may become wider as the distance from the coupling point becomes larger.
Further, in the thin-film magnetic head of the invention and method of manufacturing the same, one of the magnetic may include a third magnetic layer portion magnetically connected to the second magnetic layer portion having larger width and area than the second magnetic layer portion.
Further, in the thin-film magnetic head of the invention and the method of manufacturing the same, the first magnetic layer portion and the second magnetic layer portion may be formed in a same procedure in a same body.
Further, in the thin-film magnetic head of the invention and the method of manufacturing the same, the first magnetic layer portion, the second magnetic layer portion and the third magnetic layer portion may be formed in a same procedure in a same body.
Further, in the thin-film magnetic head in the invention and the method of manufacturing the same, the first magnetic layer portion and the second magnetic layer portion may be formed in a same procedure in a same body, and the third magnetic layer portion may be formed in a different procedure in a separate body from the first and second magnetic layer portion.
Further, in the thin-film magnetic head of the invention and the method of manufacturing the same, the third magnetic layer portion may be placed overlapping at least a portion of the second magnetic layer portion.
Further, in the thin-film magnetic head of the invention and the method of manufacturing the same, the third magnetic layer portion may go over the coupling point and be placed overlapping a portion of the first magnetic layer portion, and an edge of the third magnetic layer closer to the recording medium may be orthogonal to the extending direction of the first magnetic layer portion. In such a case, the width of the first magnetic layer portion which determines the recording track width of the recording medium is exactly constant all through the area from the orthogonally crossing point to the top area even if a concave corner of the step face in the width direction at the coupling point is rounded off, since the coupling point of the first and the second magnetic layer portion is receded from the edge face of the third magnetic layer. Here, the position of the edge surface of the third magnetic layer portion may be set in the same position of the edge of the insulating layer closer to the recording medium. In such a case, the width of the first magnetic layer which determines the recording track width of the recording medium is exactly the same all through the area so-called a throat height.
Further, in the thin-film magnetic head of the current invention and the method of manufacturing the same, at least some portion of the second magnetic layer portion may be set on the slope surface formed by an insulating layer. In such a case, even if a concave corner of the step in the width direction at the coupling point is relatively quite rounded off due to the fact that the second magnetic layer portion is formed on the slope mentioned above, and so that a condition of exposure during a procedure of a photolithography for forming the first magnetic layer portion is made worse, variance of the substantial width of the first magnetic layer can be avoided.
Another object, distinctive characters and effects of the current invention will be made clear in the following descriptions.